Generally, a multifunctional video tape recorder has not only a normal function for reproducing tapes in a normal manner, but also has special functions such as still picture reproducing, slow picture reproducing, high speed reproducing, double speed reproducing and the like. In order to perform the above-mentioned functions, the multifunctional video tape recorder is provided with two pairs of heads which are different in their head widths in the double-azimuth head type. Of the two pairs of heads, one pair are used in a standard play i.e., SP, mode while the other pair are used in a super long play i.e., SLP, mode.
Therefore, in a multifunctional video tape recorder, the reproducing head should be selected in accordance with the designation of the user, and the phase shift direction of the video signal reproduced in accordance with the head thus selected has to be controlled. The controlling of the phase shift direction of the video signal shifted occurs in the video signal reproducing processor unit. In a VHS-type video tape recorder, the phase of the video signal is advanced by 90.degree. for every horizontal line for a given track and conversely, the phase is delayed by 90.degree. for every horizontal line for the adjacent track to the given track, so that a crosstalk component of the reproduced video signal will be removed. The conventional circuit for head selecting and phase shift direction controlling is constituted as shown in FIG. 1, and this circuit will be described as to its operation below.
A microcomputer 100 generates function control data for the reproducing function designated by the user, and this data is supplied to both a servo controller 104 and a multifunctional controller 105. The servo controller 104 controls the speeds of a drum motor M1 and a capstan motor M2 through lines 2 and 3 respectively, by means of the function controlling data which is supplied from the microcomputer 100 through a bus line 1, while the servo controller 104 also controls switching operations of first and second switches SW1, SW2 through a line 4, and sends a head channel selection signal to a multifunctional controller 105.
The multifunctional controller 105 outputs an amplifier selecting signal through a line 6 in accordance with a function control data supplied through bus line 1, the head channel selecting signal supplied through line 4, and a comparing signal supplied through a line 5 from a comparator 103, while the multifunctional controller 105 also outputs a phase shift direction controlling signal through a line 7. Then the switching operation of third switch SW3 is controlled in accordance with the amplifier selecting signal.
First the normal reproducing function will be described. The normal reproducing function can be described based on a classification into the standard play mode and the super long play mode, and special reproducing can also be described based on a classification into the standard play mode and the super long play mode.
First in the case of the standard play mode in the normal reproducing function, the first switch SW1 alternately supplies to a first amplifier 101 video signals read out by first and second heads SP1, SP2 in response to the head channel selecting signal. The first amplifier 101 which receives the video signals through the first switch SW1 amplifies the video signals at a constant amplifying rate, and supplies them to the third switch SW3, while the third switch SW3 outputs the output signals of the first amplifier 101 through a line 8 in accordance with the amplifier selecting signal.
Meanwhile, the phase shift direction controlling signal is generated in response to the azimuth angle of the selected head according to the first and second heads SP1, SP2 which are alternately selected. Thus, if the first head SP1 having an azimuth angle of +6.degree. is selected, the phase shift direction controlling signal is generated as a high logic state while, if the second head SP2 having an azimuth angle of -6.degree. is selected, the phase shift direction controlling signal is generated as a low logic state.
Second, in the case of the super long play mode in the normal reproducing function, the second switch SW2 supplies to a second amplifier 102 the video signals read out alternately by third and fourth heads SLP1, SLP2. The second amplifier 102 amplifies the video signals incoming through the second switch SW2 at a constant amplifying rate to output them to the third switch SW3, while the third switch SW3 transmits the output signals of the second amplifier 102 through a line 8 in response to the amplifier selecting signal. Then each time the third and fourth heads SLP1, SLP2 are selected, the phase direction controlling signal is generated in response to the azimuth angle of the selected head. Thus, if the third head SLP1 having an azimuth angle of +6.degree. is selected, the phase shift direction controlling signal is generated as a high state while, if the fourth head SLP2 having an azimuth angle of -6.degree. is selected, the phase shift direction controlling signal is generated as a low state. Further, in the case of multifunctional reproducing functions, i.e., in the case of the special functions, the tape runs at a speed different from that of the normal reproducing function and therefore, correct readings can not be made from the tape.
Within a single time interval between the change-overs of the head channels, a plurality of video tracks will pass, and therefore, the first to fourth heads SP1, SP2, SLP1, SLP2 will move simultaneously or separately. Therefore, the heads can be selected in synchronization with the comparing signal which is the output of the comparator 103, or the heads can be selected in synchronization with the head channel selecting signal for reading out the video signals from a proper head within a single time interval. In the case of multifunctional reproducing functions, the selections of the heads are made as specified in Table 1--1 below, while the wave patterns of the amplifier selection signals and the phase shift direction controlling signals are shown in FIG. 2. Meanwhile, the heads and amplifiers selected in accordance with the head channel selecting signal and the amplifier selecting signal, and the phase shift direction controlling signal generated in accordance with them, are as shown in Table 1-2 below.
TABLE 1-1 ______________________________________ Function Video head selected ______________________________________ Normal reproducing SP: SP1, SP2 SLP: SLP1, SLP2 Still picture reproducing SP: SP2, SLP2 SLP: SP1, SLP1 Slow picture reproducing SP: SP2, SLP2, SP1 SLP: SLP1, SP1, SLP2 Double speed reproducing SP: SP2, SLP2 SLP: SP1, SLP1 High speed reproducing SP: SP1, SP2, SLP1, SLP2 SLP: SLP1, SLP2 ______________________________________
TABLE 1-2 ______________________________________ Operating Item voltage Selection Remarks ______________________________________ Head channel SP: H SP2 SP1: +6.degree. selecting L SP1 SP2: -6.degree. signal SLP: H SLP1 SLP1: +6.degree. L SLP2 SLP2: -6.degree. AMP selecting H AMP1 AMP1: SP head signal L AMP2 AMP2: SLP head Phase shift H +6.degree. direction L -6.degree. controlling signal ______________________________________
As described above, the conventional circuit for generating the head channel selecting signal and the phase shift direction controlling signal is very complicated because it selects the amplifiers and generates the phase shift direction controlling signal through a multifunctional controller 105.